An extremely versatile and successful commercial press for dewatering suspension is the press sold by Kamyr, Inc. of Glens Falls, N.Y. under the trademark RING.RTM.. The basic operating theories and components of the press are described in U.S. Pat. No. 4,534,868. Such a press may be used as a single channel press, or may have a plurality of channels, either a number of channels formed in a single rotor, or multiple rotors with channels between the rotors or in each rotor. The rotor channels are all rotatable about a common axis of rotation.
While multi-channel RING.RTM. presses are very useful and versatile, in some circumstances where they are force fed--as with screw feeders--there can be a tendency for one of the channels to be over fed, resulting in a final product which has not been dewatered to the extent necessary (e.g. no dry sludge cake when sludge is being dewatered).
The problem of overfeeding the channel with a screw feeder is solved according to the present invention by providing a means for equalizing the amount of mass fed to the channels (by equalizing the inlet pressure to the channels), the equalizing means disposed just exteriorly of the press housing at the pressure ends of the screw feeders.
In a preferred embodiment, the equalizing means comprises a module disposed between a housing for the screw feeders and the cylindrical press housing. The module comprises first and second plates, extending generally parallel to the axis of rotation of the rotors, and generally perpendicular to the direction of transport of humid mass by the screw feeders. A plurality of tubular conduits are disposed between the plates, each conduit connecting a channel to a screw feeder. The first plate is connected to the press housing and the second plate connected to the screw feeders housing. And, means are provided defining a cross over tunnel extending between each of the conduits, the cross over tunnel connected to the first plate. Each of the conduits is preferably generally circular in cross-section, and the cross over tunnel is generally quadrate in cross-section.
The invention also contemplates a method of dewatering a humid mass, particularly a method of dewatering sludge. The method comprises the steps of: (a) Positively feeding under substantial pressure the humid mass to each of a plurality of inlets to each of a plurality of annular channels as a continuous stream, each of the annular channels having perforations (in a screen liner) in at least a working section thereof. (b) Creating an axial pressure at the interior of the humid mass. (c) Continuously moving movable side wall sections of the annular channels rotationally about the axis along at least the working sections, the movable side wall sections each having a surface area greater than the surface area of the remaining side wall sections of the annular channels whereby to continuously displace the mass toroidally along at least the working sections and to generate between the movable side wall sections and the humid mass a dynamic friction force thereby creating a pressure which is inferior to the axial pressure whereby to create between the side wall section and the humid mass a low pressure zone which causes the liquid in the liquid mass to be displaced transversely to the direction of travel of the humid mass and to flow out of the annular channels through the perforations. (d) Continuously discharging the mass which contains only a small percentage of liquid at an outlet ends of the annular channels. And, (e) equalizing the amount of the humid mass fed to the annular channels at the inlets so as to minimize the chance that one annular channel will be overfed and will not produce a discharged mass with as small a percentage of liquid as desired.
It is the primary object of the present invention to provide a simple and effective apparatus and method for equalizing the amount of mass fed to the channels of a multi-channel "RING".RTM. press. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.